Single-site catalyst compounds, such as metallocenes, are often paired with methyl alumoxane or a non-coordinating anion activator to polymerize monomers, such as olefins. These catalysts are regarded as precise and often produce polymers having both narrow molecular weight distribution (Mw/Mn) and narrow composition distribution.
The precision of single-site metallocene catalysts is, however, also a limitation in that narrower distribution in polymer molecular weight and/or compositional distribution can hinder post-reactor processing. The ability to systematically control this distribution in a novel way would be useful.
It is thought that the structure of both the catalyst and the activator can affect the reactivity of the resulting activated catalyst ion pair. This can frequently lead to differences in molecular weight and comonomer content for the resulting polymer products. While multiple catalyst/activator pairings have been employed in the past, the use of a single catalyst with multiple non-coordinating anion activators has not been described.
Combinations of activators have been described in U.S. Pat. Nos. 5,153,157; 5,453,410; EP 0 573 120 B1; WO 94/07928; WO 95/14044; and “Unusual Synergistic Effect of Cocatalysts in the Polymerization of Propylene by a Zirconium Bis(benzamidinate)Dimethyl Complex” Volkis, et al., Organometallics, 2006, 25, pp. 2722-2724. These documents all discuss the use of an alumoxane in combination with an ionizing activator.
Two step activation sequences have also been described in WO 2008/146215, where alumoxane was staggered with an organylaluminum compound. Likewise, WO 00/09514 discloses tris(perfluorophenyl) aluminum combined with di(isobutyl)(2,6-ditert-butyl-4-methylphenoxy)aluminum to form two aluminum activators for (t-butylamido)dimethyl(tetramethyl-cyclopentadienyl)silanetitanium 1,3 pentadiene; or dimethylsilane bis(2-methyl-4-phenylindenyl)zirconium 1,4 diphenyl-1,3 butadiene; or (t-butylamido)(tetramethylcyclopentadienyl)dimethylsilane titanium dimethyl; or rac dimethylsilyl bis(1-indenyl) zirconium dimethyl.
Wei et al., in “Programmable Modulation of Comonomer Relative Reactivities for Living Coordination Polymerization through Reversible Chain Transfer between “Tight” and “Loose” Ion Pairs”, Angew. Chem. Int. Ed. 2010, 49, pp. 9140-9144, disclose use of diethyl zinc in combination with [PhNHMe2][B(C6F5)4].
Other references of interest include EP 0 426 637; EP 0 573 403; EP 0 277 004; EP 0 277 003; EP 0 811 627; U.S. Pat. Nos. 6,147,173; 5,387,568; 5,648,438; and U.S. 2010/0029873.
None of the above references disclose two boron containing non-coordinating anion activators to produce polymers having different populations. Likewise, none of the above references disclose combinations of Group 13 element activator complexes comprising at least one halogenated, nitrogen containing aromatic group.
In view of the above, there is a continuing need for activating cocatalyst compounds both to improve industrial economics and to provide simpler methods of synthesis and preparation of suitable polymers. Additionally, improvements in gas phase and slurry polymerization of olefins, where supported catalysts are typically used, are sought so as to meet the demanding criteria of industrial processes.